The dynamic range of a scene is determined by a ratio of the highest and lowest light levels of the scene. The dynamic range of a sensor is determined by a ratio of the highest light level in a scene that does not saturate the sensor to the lowest light level, i.e., above a noise floor, detectable by the sensor. The dynamic range of a scene may be, for example, 100,000:1, while the dynamic range of a sensor may be, for example, 100:1. When the dynamic range of the scene exceeds the dynamic range of the sensor, details in the regions of highest light levels and lowest light levels are lost.
Exposure may be adjusted in a manner such that the dynamic range of a sensor covers as much useful light level as possible. Exposure cannot increase the dynamic range of the sensor. However, combining two or more different exposures of a scene may permit the capture of a higher dynamic range of the scene then would otherwise be possible by a single exposure.
With respect to combining different exposures to produce an HDR image of a scene, various sensor manufacturers have employed various techniques to overcome the dynamic range capabilities of imaging sensors. Some techniques provide software solutions that align two images of different exposure times in order to form a higher dynamic range image than would otherwise be possible. Other techniques provide hardware solutions, e.g., modified sensors, to capture two images of a scene that will be aligned to form a higher dynamic range image.